function test
  clear all;
  close all;
  clc;

  [y, fs] = audioread('piano.wav');
  x = y(:,1);
  freqz(x);
  
  fc = 400;
  w = fc * 2 / fs;
  [len, track] = size(y);
  
  fc = [46, 94, 187, 375, 750, 1500, 3000, 6000, 12000];
  filter_output = zeros(len, 1);
  amp = [2,1,1,1,1,1,1,1,1,1];
  n = 1 : 256;
  wc = fc * pi * 2 / fs;
  for index = 1:9
      filter_output = filter_output + (amp(index + 1) - amp(index)) * sinc(wc(index) * n) / (pi * n);
  end
  freqz(filter_output);
  
  
  
  x = conv(x, filter_output);
  size(x)
  sound(x, fs);
end
